These two books, long ago separately pre-ordered, arrived from different places on the same day:
One of the things keeping me busy lately has been a Haskell reading group, which has mostly amounted to me teaching some people Haskell, using this book as the main text. We've been using the web preprint, and it's exciting to see the real thing!
For a long time, I've felt that there were lots of decent "first books" on Haskell, but not a single "second book." This is especially unfortunate, given that the most difficult part for many people of learning Haskell is making the jump from CS101 stuff to the actual state of the art. This book rectifies that. In fact, having used it with beginners, I'm not sure I'd recommend it as the best very first book on Haskell, but that hardly matters. Since a lot of this material has until now had to be painstakingly gleaned from mailing list archives, conference papers, functional pearls, blogs and sometimes IRC, this is a very welcome reference. It's exciting to see a Haskell book that goes beyond the basics.
I haven't gotten all the way through it yet, but I'd already happily recommend it. And of course it's great to see the first Scala book in print as well. I understand that 2009 will witness a number of unfortunately similarly named titles. Too bad about the names, otherwise it's a great trend. Congratulations to all six authors of these two books!